The present invention relates to projectile launching devices, and particularly to a device for accelerating a projectile to an extremely high velocity. The invention is particularly useful in artillery, anti-aircraft and tank guns, and is therefore described below with respect to this application.
Recent technology has been developed to replace gunpowder in artillery and tank guns by an inert material. One technique, called the electrothermal gun technique, is based on using electrical energy from a pulsed power supply to produce a high-temperature, high-pressure plasma arc to increase the acceleration of the projectile. According to this technique, the projectile assembly includes a conventional cartridge/projectile arrangement, the cartridge containing a central anode electrode and an annular body cathode with a solid dielectric charge, such as polyethylene or paraffin, between the two electrodes. The electrical energy from a pulsed power supply quickly vaporizes the dielectric charge to produce high-temperature and high-pressure gasses, which accelerate the projectile in a manner very similar to the combustion products generated from gunpowder.
While the above electrothermal gun technique has many advantages over gunpowder, it is subject to the same major limitation of gunpowder, namely that the maximum velocity to which the projectile can be accelerated is limited to the "escape velocity" of the hot gasses produced by the cartridge. Also, the acceleration efficiency decreases with increasing velocity.
Another technique recently developed to replace gunpowder is known as the "electromagnetic rail gun" technique, wherein the launch tube comprises a pair of conducting rails circumferentially separated by insulating spacers. When the launch tube is supplied with electrical energy, current flows through the rails and through an armature carried by the projectile assembly which slides between the rails, to generate a magnetic field around the rails. This magnetic field, together with the current flowing through the armature, produces a Lorentz force that accelerates the armature and the projectile with it. One form of electromagnetic rail gun is a D.C. rail gun in which the current flows in one direction through one rail and in the opposite direction through the other rail. In such a D.C. rail gun, the armature carried by the projectile is a plasma arc armature produced by a thin foil fuse that flashes into a conductive metal vapor when the high current is passed through it.
An advantage of the electromagnetic rail gun is that theoretically there is no limit as to the velocity attainable. However, the amount of electrical energy required is extremely high, much higher than that presently available in tanks for example.
Also known is a "hybrid" gun, including a first phase based on the electrothermal gun technique, and a second phase based on the electromagnetic rail gun technique. In such as hybrid gun, the first, electrothermal, phase is also limited by the "escape velocity" and its efficiency also drops with increasing velocity; whereas in the second, electromagnetic rail gun phase, considerable power is required.